A dandelion-like carbon microsphere/MnO2 nanosheets composite for supercapacitors

This article reported the electrochemical performance of a novel cabon microsphere/MnO₂ nanosheets (CMS/MnO₂) composite prepared by a in situ self-limiting deposition method under hydrothermal condition. The results of scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that MnO₂ nanosheets homogeneously grew onto the surface of CMS to form a loose-packed and dandelion-like core/shell microstructure. The unique microstructure plays a basic role in electrochemical accessibility of electrolyte to MnO₂ active material and a fast diffusion rate within the redox phase. The results of cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectrometry indicated that the prepared CMS/MnO₂ composite presented high capacitance of 181 F·g⁻¹ and long cycle life of 61% capacity retention after 2000 charge/discharge cycles in 1 mol/L Na₂SO₄ solution, which show strong promise for high-rate electrochemical capacitive energy storage applications.     

四种晶型MnO2超级电容器电极材料的电化学性能研究

用尽量简便的方法制备出δ、α、β及γ型4种MnO₂粉末. 通过X射线衍射（XRD）、场发射扫描电镜（FSEM）、热重分析（TGA）与比表面积测试（BET）等方法对样品粉末性质进行分析,并对4种不同粉末制成的电极进行循环伏安、恒流充放电及稳定性测试. 结果表明,4种MnO₂都具有良好的电容特性,其中α-MnO₂具有最高的比表面积与孔隙率,故其电极比容量最高,但其大电流放电时的倍率特性较差. 其余3种MnO₂比表面积相当,而β-MnO₂虽然比容量较低,但其简单的孔隙结构使其拥有最好的倍率特性与稳定性.     

MnO2的离子交换行为及其离子筛法提取锂

锂在受控核聚变反应中的应用以及高能锂电池的出现，显示了其在解决能源问题的重要意义．但当前查明的锂矿石贮量不大，近年来，人们已开展有关从海水中提取锂的研究．在电解质溶液中ＭｎＯ２表面具有离子交换特性［１］，以ＭｎＯ２和ＬｉＯＨ制得的离子筛型吸附剂，对海...     

Kinetics of anodic formation and cathodic reduction of MnO2 in the sulfate electrolyte solutions

The anodic formation of manganese dioxide is studied voltammetrically in a wide range of potential scan rate (V = 0.001–8 V/s). Using the diagnostic criteria of cronovoltammetric method, based on the original experimental data, the mechanism of electrooxidation of manganese ions in the acidic medium with subsequent reaction of disproportionation of the product of irreversible electrode reaction and hydrolysis yielding manganese dioxide is proposed. The kinetics of cathodic reduction of electrolytic manganese dioxide in the 0.5 M Na₂SO₄ solution is studied under the steady-state and non-steady-state potentiodynamic polarization conditions. From the experimental data, it is found that, in the acidic medium (pH 1–3), the mechanism of the electrode process changes depending on the cathodic potential scan rate: at the scan rate V < 0.5 V/s, MnOOH forms via one-electron transition leading, in its turn, to the partial deactivation of electrode surface with subsequent disproportionation of manganite. At the relatively high potential scan rates, manganite has no time to form, and the two-stage reduction via one-electron transitions at each stage is well pronounced. The parameters of the electrode processes are calculated.     

Water-in-salt electrolyte ion-matched N/O codoped porous carbons for high-performance supercapacitors

Pore size and distribution in carbon-based materials are regarded to be a key factor to affect the electrochemical capacitive performances of the resultant electrodes.In this study,nitrogen and oxygen codoped porous carbons(NOPCs) are fabricated based on a simple Schiff-base reaction between m-phenylenediamine and terephthalaldehyde.The NOPCs have tunable morphologies,high surface areas,abundant heteroatom doping.More importantly,the carbons show a dominant micropores of 0.5-0.8 nm,comparable to the ionic sizes of LiTFSI(Li^+0.069 nm;TFSI-0.79 nm) water-in-salt electrolyte with a high potential window of 2.2 V.Consequently,the fabricated symmetric supercapacitor gives a high energy output of 30.5 Wh/kg at 1 kW/kg,and high stability after successive 10,000 cycles with ^96.8% retention.This study provides promising potential to develop high-energy supercapacitors.     

Application of Rhamnolipids as Dispersing Agents for the Fabrication of Composite MnO2-Carbon Nanotube Electrodes for Supercapacitors

The high theoretical capacitance of MnO₂ renders it a promising material for the cathodes of asymmetric supercapacitors. The good dispersion of MnO₂ and conductive additives in a nanocomposite electrode is a key factor for efficient electrode performance. This article describes, for the first time, the application of rhamnolipids (RL) as efficient natural biosurfactants for the fabrication of nanocomposite MnO₂-carbon nanotube electrodes for supercapacitors. RL act as co-dispersants for MnO₂ and carbon nanotubes and facilitate their efficient mixing, which allows for advanced capacitive properties at an active mass of 40 mg cm⁻² in Na₂SO₄ electrolytes. The highest capacitance obtained from the cyclic voltammetry data at a scan rate of 2 mV s⁻¹ is 8.10 F cm⁻² (202.6 F g⁻¹). The highest capacitance obtained from the galvanostatic charge–discharge data at a current density of 3 mA cm⁻² is 8.65 F cm⁻² (216.16 F g⁻¹). The obtained capacitances are higher than the capacitances of MnO₂-based electrodes of the same active mass reported in the literature. The approach developed in this investigation is simple compared to other techniques used for the fabrication of electrodes with high active mass. It offers advantages of using a biocompatible RL biosurfactant.     

网络结构的聚苯胺-二氧化锰纳米复合材料的制备及其电化学性能

利用水热法合成了一维的MnO2纳米棒,经十六烷基三甲基溴化铵(CTAB)表面改性后与苯胺单体在低温下混和,通过原位化学氧化聚合法制备了聚苯胺-二氧化锰(PANI-MnO2)纳米复合材料.采用FESEM、FT-IR、XRD、TG、循环伏安以及恒电流充放电等测试技术对复合材料进行了结构和性能的分析.结果表明:MnO2纳米棒...     

非水介质中Zn—MnO2的可充性研究

报道了以尖晶石型二氧化猛为正极，１ｍｏｌ／Ｌ＾－１Ｚｎ（ＣｌＯ４）２的碳酸丙烯酯为电解液构成Ｚｎ－ＭｎＯ２二次电池体系的充放电性质和反应机理分析。结果表明，这一体系的充放电过程表现为Ｚｎ在λ－ＭｎＯ２中的电化学嵌入和脱嵌反应。     

MnO2电沉积直立碳纳米管制备超级电容器的研究

以直立碳纳米管为基底,以pH=6.0的0.1mol/L Na2SO4 为底液,采用电化学沉积法在0.2 mol/L Mn(CH3COO)2溶液中制备了直立碳纳米管与二氧化锰复合材料。SEM测试结果表明复合材料表面呈现多孔状结构。通过循环伏安,恒流充放电,交流阻抗等电化学方法对复合材料修饰电极进行电容性质测试。实验结果表明,在1mol/L KCl 溶液中,0-0.6V(vs. 银/氯化银参比)电位窗口内此复合材料表现出优良的超电容性能。直立碳纳米管电极的比电容为16 F/g,在碳纳米管表面沉积上二氧化锰修饰层后,此复合材料电极的比电容增大至330 F/g,比电容量大幅提升近20倍。同时扫描200圈后,直立碳纳米管与二氧化锰复合材料的循环伏安曲线变化很小,说明其具有相当好的循环寿命和电容稳定性能。     

High voltage supercapacitors using hydrated graphene film in a neutral aqueous electrolyte

The potential stability windows of chemical converted graphene in different aqueous electrolyte solutions were investigated for the first time. Based on this result, a supercapacitor with a high voltage and long cycle-life was prepared with the hydrated graphene films in the neutral aqueous solution at the maximum voltage of 1.6 and even 1.8 V. The electrochemical performance of the obtained sample was systematically investigated by cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. According to the cyclic voltammetry, hydrated graphene film can still retain rectangular shape at the high scan rate of 0.5 V/s in the neutral aqueous electrolyte. At a galvanostatic charge/discharge rate of 1 or 200 A/g, the specific capacitance of 202.3 or 138.1 F/g was delivered, respectively. Furthermore, the EIS results also confirm its fast neutral ion diffusion and high operating frequency of 9.34 Hz.     

水热处理对二氧化锰电容性能的影响

采用化学共沉淀法制备了二氧化锰。XRD测试表明，产物为α-MnO₂和γ-MnO₂无定形粉末，经水热处理后的二氧化锰晶化程度增加，为α-MnO₂和γ-MnO₂混晶相结构。电化学测试表明，二氧化锰单电极比容量达252.72 F·g^-1。经水热处理后单电极比容量达到299.15 F·g^-1，比处理前的提高18.37%。经400次循环后，水热处理后的样品比容量衰减极小。     

热处理对线团状二氧化锰结构及其电化学性质的影响

以氯化锰与高锰酸钾为原料, 在低浓度下大数量合成由无数片状纳米层组成的线团状二氧化锰粒子. 采用X衍射, 扫描电镜, 液氮等温吸附脱附、循环伏安、交流阻抗及恒流充放电等方法研究了温度对产物结构及电化学性质的影响. 结果表明处理温度升高, 微孔减少, 比表面积减小, 孔径变大, 在300 ℃以下二氧化锰粒子的结构保持无定型结构. 交流阻抗测试显示随着处理温度的升高, 样品的法拉第电荷传递能力和离子在电解液与活性材料界面的扩散能力均得到提高. 比电容测试显示在200 ℃处理的二氧化锰具有最高的比电容, 以1 mol·L^-1 Na₂SO₄为工作介质, 扫速为2 mV·s^-1时, 其比电容是210.6 F·g^-1. 该研究表明: 材料的电化学性质可以通过热处理进行调整, 适当的热处理能提高该材料作为超级电容器活性材料的性质.     

炭载二氧化锰的制备和锂离子超级电容器性能的研究

制备了炭气凝胶载二氧化锰(AG-MnO₂)复合材料, 材料物理化学表征表明, 在炭气凝胶表面和微孔内沉积二氧化锰, 改善了炭气凝胶的电化学性能. 以炭二氧化锰复合材料为负极, LiMn₂O₄为正极, 设计出一种新型的高能量密度混合电容器, 并研究了负极工作电位范围对电容器性能的影响. 研究结果表明, 引入高容量的AG-MnO₂复合材料, 并通过扩大负极工作电位区间, 可设计出能量密度高达92 Wh•kg^－1(基于正负极活性质量)的混合电容器, 为炭对称电容器的5倍. 这种混合电容器经过1000次循环, 容量仍然保持在80%以上.     

合成路径对超级电容器用二氧化锰性质的影响

研究了不同合成路径对二氧化锰结构及电化学性能的影响. 路径1为将0.15 mol/L醋酸锰溶液加入到0.1 mol/L高锰酸钾溶液中; 路径2中, 物料的加料方式与路径1相反. X射线衍射和扫描电镜测试表明合成的产物均为无定型α-MnO2, 晶粒尺寸为200～300 nm. 氮吸附曲线测试结果表明: 路径1所得的二氧化锰具有较大的比表面积(329 m2/g), 其孔径分布比较均一, 孔径6～12 nm, 孔体积较小(0.45 cm3/g); 路径2所得的二氧化锰比表面积较小(298 m2/g), 具有从微孔到大孔的连续分布孔, 平均孔径11.4 nm, 孔体积较大(0.66 cm3/g). 交流阻抗和循环伏安电化学测试结果显示: 路径2所得样品具有较大的法拉第阻抗, 在较低扫描速度下(2 mV&#8226;s－1), 其比电容(203 F&#8226;g－1)比路径1所得MnO2高(189 F&#8226;g－1), 路径1所得二氧化锰的比电容随扫描速度变化的趋势较小. 恒流充放电测试显示路径1合成的二氧化锰具有较好的功率特性. 在2 A&#8226;g－1的电流密度下, 其比容量为0.1 A&#8226;g－1电流密度下的96.3%, 而路径1的样品的容量保持率为92.5%. 造成上述结果差异的原因是由于不同合成路径导致二氧化锰存在不同的孔结构特征所致.     

Chemiluminescence of Colloidal MnO2 with Luminol and Determination of Polyhydroxyl Compounds

The reaction between luminol and colloidal MnO₂ (prepared by chemical reduction of KMnO₄ with Na₂S₂O₃ under neutral aqueous condition) produced an intense chemiluminescence (CL) emission in alkaline medium. The CL reaction conditions were carefully optimized and the CL reaction mechanism was thoroughly discussed. Manganese(III) was suggested to be involved in the reaction and 3‐aminophthalate anion was the luminophor. Moreover, the effects of 23 compounds on the colloidal MnO₂‐luminol CL system were investigated to explore its possible analytical applications. Polyhydroxyl compounds were observed to inhibit the signal significantly, whereas sulfhydryl compounds enhance it slightly. The analytical figures for five polyhydroxyl compounds, namely ascorbic acid, rutin, pyrogallol, quercetin, and L‐adrenaline, were presented. As a preliminary application, the method was applied to the determination of rutin in pharmaceutical formulations.     

TiO2 nanotubes fabricated by electrochemical anodization in molten o-H3PO4-based electrolyte: Properties and applications

Self-organized TiO₂ nanotubes (NTs) can be formed by electrochemical anodization. Anodization is generally performed in aqueous or organic electrolytes containing halogen ions, such as Cl⁻ and F⁻. However, these electrolytes lead to less ordered structures or carbon remnants, thus suppressing the electrical properties and limiting the applications. To overcome these limitations, new anodization approaches were performed in carbon-free electrolyte-based electrolyte. In this review, we summarizes the short history of TiO₂ NTs, general mechanisms of growing NTs, properties, and applications of classic TiO₂ NTs. Then, a new-generation of anodization approach conducted in molten orhto-phosphoric acid is elucidated based on anodization parameters, concluding the optimized condition to form highly ordered TiO₂ NT arrays. Finally, the review addresses further modifications such as heat-treatment, noble metal deposition, thermal dewetting, and double anodization to enhance the optical and electrical properties for use in various applications.     

多孔不锈钢基二氧化锰薄膜电极的制备及电容特性

用电化学方法制备了一种多孔不锈钢基二氧化锰薄膜电极。 在不锈钢基体上以聚乙二醇辛基苯基醚（Triton X-100）在水溶液中形成的液晶作掩膜,通过电化学腐蚀制备了多孔基体电极,用恒电位方法在基体上沉积二氧化锰薄膜。 用扫描电子显微镜对二氧化锰薄膜电极形貌进行了考察,循环伏安法和充放电曲线法测试了二氧化锰薄膜电极的电容。 结果表明,腐蚀后的不锈钢基体呈现多孔特征,孔分布无规律,孔径大小从几十纳米到几百纳米不等,沉积的二氧化锰呈颗粒状,直径为80~90 nm。 扫描速率为20 mV/s,沉积电量0.4 C/cm2时,循环伏安法测得的二氧化锰薄膜电极的质量比电容达400 F/g;沉积电量4~5 C/cm2时,面积比电容达到320 ×10-3 F/cm2,此时的质量比电容仍保持在200 F/g左右。 实验结果表明,多孔不锈钢基二氧化锰薄膜电极在超级电容器领域有潜在的应用前景。     

MnO2纳米线支撑中空十二面体CoNi2S4的制备及其电化学性能

采用简单的室温搅拌法和一步硫化法制备了 MnO₂纳米线支撑中空十二面体 CoNi₂S₄ (MnO₂/CoNi₂S₄)电极材料。超长MnO₂纳米线为电子转移提供了直接路径,而且其较大的长径比有利于形成自支撑的三维导电网络结构;中空多孔的CoNi₂S₄提供了更丰富的活性位点,同时缓解了充放电过程中的体积变化。得益于以上优势,MnO₂/CoNi₂S₄在1 A·g^-1时具有1 531.1 F·g^-1的比电容,在 10 A·g^-1时具有 86.9% 的电容保持率。利用 MnO₂/CoNi₂S₄作为正极、活性炭(AC)为负极组装的 MnO₂/CoNi₂S₄||AC器件实现了高能量密度(800 W·kg^-1时40 Wh·kg^-1)和优异的循环稳定性(5 000次循环后保持64.8%)。